A data writable optical disc, such as a DVD±R and a DVD±RW, conventionally includes not only a single-layer disc with one recording layer formed in which record data is recorded, but also a multilayer disc with a plurality of recording layers. For example, currently commercialized discs are a single-sided, single layer type DVD provided with only one recording layer, a single-sided, dual layer type DVD provided with two recording layers on one side, and the like. The single-sided, single layer type DVD has a maximum recording capacity of about 4.7 GB, while the single-sided, dual layer type DVD has a maximum recording capacity of about 8.5 GB. As described above, as the number of recording layers increases, the maximum recording capacity of the optical disc increases.
By the way, a recording/reproducing apparatus, which can perform the recording of the record data and the reproduction of the recorded record data on the aforementioned multilayer disc, normally records the record data into only one recording layer in the process of recording the record data, and it does not perform anything on the other recording layers. For example, the recording/reproducing apparatus performs such a recording process that the record data is recorded into an entire first recording layer (or L0 layer) before the record data is recorded into a second recording layer (or L1 layer). Therefore, although the maximum recording capacity of the optical disc increases, a recording speed with respect to the multilayer disc is not different from a recording speed with respect to the single layer disc. Incidentally, the recording speed with respect to the single layer disc (in other words, the recording speed with respect to one recording layer) is considered to be limited to be about 16 times (in case of a DVD) larger than a reference recording speed (or 1-time recording speed) because of mechanical properties or the like of the recording/reproducing apparatus and the optical disc.
A patent document 1 discloses a technology in which an initialize process is performed simultaneously on two recording layers, with regard to the initialize process of the multilayer disc.
Patent document 1: Japanese Patent Application Laid Open NO. 2004-22116